Electron discharge device and circuit



Sept. 13, 1938. w. 1.. MEIER 2,130,191

ELECTRON DISCHARGE DEVICE AND CIRCUIT Filed Jan. 25, 1958 INVENTOR.W/LBER L. MEIER ATTORNEY.

Patented Sept. 13, 1938 UNITED S 'l'ATES PATENT OFFICE,

ELECTRON DISCHARGE DEVICE AND CIRCUIT Wilber L. Meier, North Arlington,N. 1., a-ignor,

assignmen bymesne ts,iolladlo0orporation oi America, a corporation ofDelaware Application January :5, 1938, Serial No. 186,789

5 Claims.

My invention relates to devices for amplifying direct currents and usingelectron discharge tubes having a gaseous atmosphere and capable ofbeing continuously controlled.

The present application is a continuation in part oi my copendingapplication, Serial No. 133,300, filed March 2'1, 1937 and assigned tothe same assignee as the present invention.

In the conventional grid controlled vacuum.

tubes provided with a thermionic cathode, control grid and anode, thespace charge which builds up around the cathode makes necessary the useof comparatively high voltages, such as volts or more, for obtainingcurrent sumciently large for practical purposes. It is also Qnecessarytouse comparatively large grid voltage swings to produce usable variationsin the output of the tube. Thus, in the. conventional high vacuum tubescomparatively large transconductances are not easily obtainable nor canlarge anode currents be'obtained with small anode voltages. It has beenrecognized that by introducing a gas in a tube and ionizing the gas thespace charge around the cathode could be neutralized and thus largeanode currents obtained with the usual anode voltages. However, in theconventional grid controlled tube containing gas, ionization of the gascauses the control grid to lose its control of the electron stream sothat while initiation of ionization can be controlled the current cannotbe controlled by the control electrode after ionization takes place.Furthermore, in these types of tubes comparatively high voltages, muchabove ionization voltages, are applied between the anode and cathode tocause a gas discharge between the anode and the cathode. Thus whilecomparatively high currents can be obtained the loss of grid control andthe necessity for high anode-cathode voltages limits the application ofthis type of tube and prevents its use in conventional radio circuits.

It is the principal object of my invention to provide a deviceparticularly suitable as a direct current amplifier and utilizing animproved electron discharge device of the continuously controlled gastype depending upon gas ionization for operation and described andclaimed in my copending application identified above.

The tube described in my copending application above identified has anenvelope containing the electrodes immersed in a gas at a low pressure.The space between the cathode and the anode is ionized to neutralize thespace charge and thus make available a large number of electrons. Only avery small voltage of the order of 6 volts, for example, which isconsiderably below ionizing voltage may be applied between the anode andcathode to obtain a comparatively large anode current. The flow ofelectrons from the cathode to the anode can then be continuouslycontrolled by an electrode to which may be applied comparatively smallvoltage swings inasmuch as there is no gas discharge between the maincathode and the anode. To produce the ionization of the gas between thecathode and anode an auxiliary cathode may be employed. A discharge isestablished between this auxiliary cathode and anode electrode, theelectrode being so positioned that the space between the main cathodeand the anode is in the path of the auxiliary discharge initiatedbetween the auxiliary cathode and its cooperating electrode.

In the tube described in the above identified ccpending applicationthere'is mounted within an envelope containing gas at low pressure, astraight indirectly heatedcathode surrounded by a cylindrical anodeclosed at both ends. An aperture, preferably covered by a mesh material,is provided at one end of the anode. Registering with this aperture area control grid and an aux iliary cathode for supplying the electronswithin the anode to ionize the gas between the main cathode and theanode. The auxiliary cathode, grid and the aperture covered by meshmaterial are all spaced less than the mean free path of electrons in thegas so that no ionization takes place between these electrodes. Thisarrangement permits continuous grid control oi! the ionization withinthe main anode. A voltage less than that required to produce ionizationis applied between the main cathode and the main anode. A voltagesumciently high to cause the electrons to have a great enough velocityin entering the space between the main cathode and the main anode isapplied between the auxiliary cathode and the main anode, the controlvoltage being applied through an input circuit to the control grid.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, but theinvention itself will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFigure 1 is a vertical section in perspective of an electron dischargedevice of the type described above, Figure 2 is a section along 22 ofFigure 1 showing details of construction, and Figure 3 is a diagrammaticshowing of a direct current amplifier arrangement made according to myinvention and using a tube of the kind shown in Figure 1.

The tube shown in Figure 1 includes an envelope I containing a gas atlow pressure for example between 150-600 microns pressure. Helium atpressures between 250 and 300 microns is very satisfactory. A stem IIsupports the electrode mount assembly within the envelope. The electrodemount assembly comprises an indirectly heated cathode I2 enclosed withina cylindrical anode I3 provided with a screen covered aperture I4 andclosed ends I5 and I6. Aperture I4 is to provide a gas communicationbetween the interior of the anode and the inside of the envelope. Thecathode I2 is insulatingly supported from the upper closed end I6 of theanode by means of the insulating bushing II. The lower end I5 isprovided with an aperture I! covered with foraminous or mesh materialI8, the shape of this aperture being best shown in Figure 2. The cathodeI2 and anode I3 are the main discharge electrodes between which theoutput current passes.

In order to neutralize the space charge around the cathode I2 duringoperation of the tube I provide an auxiliary electrode system comprisingan indirectly heated cathode and grid in registry with the aperture I8to project electrons from the auxiliary cathode into the spacesurrounding the cathode I2.

This electrode system comprises an indirectly heated auxiliary cathodeI9 supported and electrically connected to the metal disc 20.Insulatingly separated from the disc by means of an insulating discmember 2| having an aperture 22, in which the cathode I9 is positioned,is a grid comprising a metallic disc member 23 having an aperture 24covered with a mesh material 24', this aperture being in registry withthe aperture I8 in the lower end of the anode. This grid is insulatinglyseparated from the anode by means of the insulating disc 25 having anaperture 26 in registry with the aperture I8. This whole mount assemblyis supported from the stem II by means of the supports and leads 21, 28and 29 connected respectively to the cathode disc, grid disc and anode.The main cathode I2 is provided with a lead 30.

In operation a low voltage less than that required for maintainingionization is applied between the main cathode I2 and anode I3 so that agas discharge cannot take place between these electrodes. Voltages areapplied between the auxiliary cathode I9 and the anode I 3, which arehigh enough to cause electrons from the cathode to be projected throughthe aligned apertures into' the space around the cathode I2 withsufiicient velocity to ionize the gas and thus neutralize the spacecharge. The grid 23 may have applied to it a control voltage which willcontrol the flow of electrons from the auxiliary cathode I5 intothespace surrounding the main cathode I2 to thereby control theionization and hence the current from cathode I2 to anode I3.

According to my invention I provide a D. C. amplifier comprising aself-excited oscillating circuit which can be used to provide a highvoltage D. C. output source from a low voltage D. C. source. In Figure 3the cathode I2 is connected through the low voltage D. C. source orbattery 40 to one side of the inductance 4|, the other side of which isconnected through an output resistor 42 to the auxiliary cathode IS. The

voltage obtained from battery 40 is less than that required to maintainionization between cathode I2 and anode I3. An intermediate point of theinductance 4| is connected by means of conductor 43 to the anode I3. Thegrid 23 may be connected to the cathode. A condenser 44 connected acrossa part of the inductance 4I furnishes with the inductance 4| anoscillating circuit. The output resistor 42 is shunted by av filtercondenser 45. In order to start oscillations a resistance 46 and switch'41 is provided.

To shock the system'into operation switch 41 is momentarily closedcausing a flow of current through the right hand portion of inductanceH, which in turn induces a voltage across the left hand portion ofinductance 4| and condenser 44. The resistance 46 may have any suitablevalue for limiting the current to a desired amount. This voltage whichis stepped up by proper ratio of turns of the two portions ofinductances 4| acting as an auto transformer is applied between thecathode I9 and the anode I3 and causes electrons to discharge into thespace surrounding the cathode I2 causing ionization which neutralizesthe space charge thereby permitting a large flow of current between thecathode I2 and anode I3. This current flowing through the right handportion of the inductance 4| again feeds back energy to the left handportion producing a regenerative action so that the system is maintainedin oscillation. Due to the rectifying action between the cathode I9 andanode I8, rectified voltages appear across the output resistance 42, thecondenser acting as a filter so that substantially uniform D. C. voltageappears across this output circuit comprising resistor 42 and condenser45. By proper circuit constants a step-up voltage can be provided acrossthe D. C. output terminals.

While I have indicated the preferred embodiment of my invention of whichI am now aware and have also indicated only one specific application forwhich my invention may be employed, it will be apparent that myinvention is by no means limited to the exact forms illustrated or theuse indicated, but that many variations may be made in the particularstructure used and the purpose for which it is employed withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What I claim as new is:

1. An electron discharge device having an en velope containing a gas, athermionic cathode within said envelope for emitting electrons, an anodefor receiving electrons from said cathode and means for ionizing thespace between the thermionic cathode and the anode and including anauxiliary cathode for providing an electron discharge in the spacebetween the thermionic cathode and anode, an inductance, and a source ofvoltage less than that required for producing ionization between saidthermionic cathode and anode and connected between the thermioniccathode and one side of said inductance, and a load connected betweenthe other side of said inductance and the auxiliary cathode, and a.connection between the anode and an intermediate point on saidinductance.

2. An electron discharge device having an envelope containing a gas, athermionic cathode within said envelope and an anode spaced from saidcathode, and an auxiliary cathode for providing an electron dischargebetween the thermionic cathode and anode to ionize the space between thethermionic cathode and anode, an inductance and a source of voltage lessthan that required to produce ionization between the thermionic cathodeand anode connected between the thermionic cathode and anode, a secondinductance and a resistor connected between the anode and the auxiliarycathode, said inductances being so positioned that current flowing inthe inductance connected between the anode and the thermionic cathodewill induce a voltage in the inductance connected between the anode andthe auxiliary cathode.

3. An electron discharge device having an envelope containing a gas, athermionic cathode within said envelope for emitting electrons, a hollowanode surrounding said thermionic cathode for enclosing the spacebetween said thermionic cathode and the anode, and means for ionizingthe space between the thermionic cathode and anode and including anauxiliary cathode, an inductance, a source of voltage connected betweenone end of said-inductance and said thermionic cathode, said source ofvoltage being less than that required to produce ionization between thethermionic cathode and anode, a resistor connected between the auxiliarycathode and the other end of said inductance, and a connection betweenthe anode and an intermediate point on said inductance, and a condenserconnected between the intermediate point on said inductance and the endof said inductance connected to said resistor.

4. An electron discharge device having an envelope containing a gas, athermionic cathode within said envelope for emitting electrons, a hollowanode surrounding said thermionic cathode for enclosing the spacebetween said thermionic cathode and the anode, and means for ionizingthe space between the thermionic cathode and anode and including anauxiliary cathode and an inductance, a source 01' voltage connectedbetween one end of said inductance and said thermionic cathode, saidsource of voltage being less than that required to produce ionizationbetween the thermionic cathode and anode, a resistor connected betweenthe auxiliary cathode and the other end of said inductance, and aconnection between the anode and an intermediate point on saidinductance, and a condenser connected between the intermediate point onsaid inductance and the end of said inductance connected to saidresistor, and a resistor and a switch connected between the anode andthe thermionic cathode.

5. An electron discharge device comprising an envelope containing a gas,a thermionic cathode within said envelope, a hollow anode surroundingsaid thermionic cathode to enclose the space between said thermioniccathode and said anode and having an aperture provided in said hollowanode, an auxiliary cathode positioned in registry with said aperturefor supplying an electron discharge between the thermionic cathode andanode to ionize the gas between said thermionic cathode and anode, aninductance, a source of voltage vonnected between one end of saidinductance and said thermionic cathode and said source of voltage beingless than that required to produce ionization between the thermioniccathode and anode, a resistor connected between the other end of saidinductance and said auxiliary cathode, and a condenser connected acrosssaid resistor, a connection between an intermediate point on saidinductance and said anode, and a condenser connected between saidintermediate point and between the resistor and the end ofsaidlnductance, and a switch and a resistor connected between the anodeand the thermionic cathode.

W'ILBER L. MEIER.

